Symptoms
- Breaker trips shortly after furnace starts
- May trip immediately on startup or after running a while
- Resetting the breaker doesn't hold
Likely causes
- CommonFailing blower motor drawing excess currentA worn motor can overheat and pull more amps than the circuit allows.
- CommonShort circuit in furnace wiringDamaged or chewed wiring can cause a direct short that trips the breaker instantly.
- PossibleFailing capacitorA weak capacitor makes the motor struggle to start, spiking current draw.
- PossibleBreaker itself worn outBreakers can weaken with age and trip below their rated load.
- Less commonDebris or a jam inside the blower housingSomething physically blocking the fan can overload the motor.
What to do
- Reset the breaker once; if it trips again immediately, turn the furnace off at its switch and leave the breaker off.
- Check the filter and blower compartment for anything visibly blocking the fan.
- Don't reset the breaker repeatedly; this can damage components further and is a fire risk.
- Note whether it trips instantly at startup or after running for a while, as this helps a technician diagnose it faster.
- Call an electrician or HVAC technician to test the blower motor, capacitor, and wiring.
When to call a pro
Call an HVAC technician or electrician if the breaker trips more than once; this points to a motor or wiring fault that needs proper diagnosis.
Safety
Use caution
Repeatedly resetting a tripping breaker risks electrical fire; if it trips more than once, leave it off and call a professional.